NASHVILLE, Tenn. >> He was once reported to the police in Illinois for stashing an AR-15 in the trunk of his car and then diving into a public pool wearing a women’s pink housecoat. There was the time he complained to an officer that the singer Taylor Swift had demanded a rendezvous. And then in July he was grabbed by the Secret Service when he tried to force his way on to the White House grounds.

Travis Reinking, 29, was on the radar of law enforcement well before he was taken into custody today and accused of barging into a Nashville Waffle House over the weekend and opening fire, killing four and injuring four more.

Yet even after the Illinois police revoked his firearms license and ordered that his guns be transferred to his father, Reinking got them back, including the AR-15 used in the Tennessee shooting, police said. His case raises questions over how such a troubled individual could have legally carried weapons for so long and could have continued to carry them even after he was ordered to give them up.

“We have a man who has exhibited significant instability,” acknowledged Don Aaron, a spokesman for the Metropolitan Nashville Police Department.

The police say that Reinking’s father, Jeffrey, the owner of a crane business near the town of Morton, Illinois, returned the guns to his son, enabling Travis Reinking to carry out the killings over the weekend.

Jeffrey Reinking’s act of returning the guns to his son is “potentially a violation of federal law,” Marcus Watson, a special agent with the Bureau of Alcohol, Tobacco, Firearms and Explosives, said at a news conference.

Jeffrey Reinking could not be reached for comment Monday. After Travis Reinking’s arrest in Washington in 2017, the FBI passed on information about him to local officials in Illinois, where he was ordered to complete 32 hours of community service at a Baptist church near Morton. The FBI closed its investigation of Reinking in October.

About 160 law enforcement officials were involved in the search for Reinking, who officials said began his rampage at the restaurant southeast of downtown Nashville just before 3:30 a.m. Sunday. The episode unnerved one of the largest cities in the South, focusing attention yet again on the ease with which so many people, including those with mental health issues, can access guns.

Reinking was seized Monday afternoon in a wooded area less than a mile from the Waffle House. He was wearing a backpack containing a loaded handgun, but Nashville police said he surrendered without incident. Officials said he was refusing to speak to detectives.

The police also said Monday that Reinking had stolen a BMW last week after posing as a customer at a local dealership, and eluded officers in a chase.

Officials identified those who were killed as Akilah Dasilva, 23; DeEbony Groves, 21; Joe R. Perez, 20; and Taurean C. Sanderlin, 29. Officials said there would have been greater bloodshed had a 29-year-old customer, James Shaw Jr., not wrested the rifle away from Reinking while he was reloading. Reinking fled the restaurant after the attack, the police said, naked except for a green jacket.

Reinking is white, and the four victims were either African-American or Hispanic, but Mayor David Briley of Nashville said he had no reason to believe that these were racially motivated killings. Instead, Briley said, there was “enough indication that there was some element of mental illness associated with it.”

Reinking lived in Illinois for most of his life and only recently moved to the Nashville area to work in construction.

In reports, the sheriff’s department in Tazewell County, Illinois, had described Reinking as a man who was hostile to the police, had threatened suicide and believed his family was harassing him.

His father, mother and grandmother were all worried enough about his behavior that they called for help. They told police that Reinking had been having delusions since August 2014.

In May 2016, police officers responded to a CVS parking lot in Morton after Reinking’s family reported that he had talked of killing himself, and owned firearms. Reinking told officers that Swift had stalked him and hacked into his Netflix account.

A few weeks earlier, he told officers, he had chased Swift in an attempt to get her to stop harassing him. “Travis stated he was telling the truth and he had proof on his phone since it was hacked,” the report said. “However, Travis would not show us his phone.”

Reinking was transported to a hospital to be evaluated. In June 2017, police were called to a public pool in Tremont, Illinois, where he had dived into a pool wearing a housecoat, then had shed the coat, wearing only underwear.

According to the report, Reinking began yelling at lifeguards and then “showed his genitals, saying he was a man.”

Still, he was not arrested.

“This is an informational report showing the state of mind of Travis Reinking,” the report noted. When the police contacted Reinking’s father, he said that he had taken three rifles and a handgun away from his son “when Travis was having problems,” then gave them back to him.

The officers advised Jeffrey Reinking that “he might want to lock the guns back up until Travis gets mental help, which he stated he would.”

In August 2017, Travis Reinking, driving a blue Mitsubishi, pulled up alongside a police car and said he wanted to file a report. About 20 to 30 people were hacking into his phone and computer, he told police. He could hear people outside his home barking like dogs, but didn’t know who they were. At a Walmart recently, he felt that a man in a black shirt was watching him, and no one else.

“Travis said he is tired of people messing with him,” the report said. The officer advised Reinking to call the police if he heard people barking like dogs again. “No further action is being taken,” the report said.

Later that month, after the White House incident, police approached Reinking and his father to deliver a copy of the paper revoking his license. He handed over the card and helped the police retrieve all of his weapons and ammunition, which were handed over to Jeffrey Reinking.

“Jeffrey was advised that he needed to keep the weapons secure and away from Travis,” the police report said. “Jeffrey stated he would comply.”

According to Illinois gun law, a person must be granted a Firearm Owners Identification card, or FOID, to possess a firearm. About 2.1 million people in Illinois have the cards.

But under the law, the process to keep firearms out of the hands of a person whose card has been revoked is weak, allowing many people to keep access to the weapons with little threat of enforcement or penalty.

The Illinois State Police revoked more than 11,000 cards in 2016, said a spokesman, Lt. Matthew Boerwinkle. People whose cards have been revoked are required to surrender the card and any weapons to a local law enforcement agency. But there is a provision that allows people whose license has been revoked to transfer their weapons to another person with a valid card, as Reinking’s father had.

Those local police departments are then required to document that the person has turned over the card and weapons.

But local law enforcement agencies frequently fail to take action. In 2016, only about 4,000 of the 11,000 people whose cards were revoked submitted the mandatory reports explaining what they did with their guns, The Chicago Tribune reported in 2017.

“They’re required to do it, but there’s essentially no teeth in the law that holds the law enforcement agencies accountable to do it,” Boerwinkle said Monday.

There is nothing in the law requiring that the person holding the weapons must lock them up, or even live in a different house than the person whose FOID card was revoked, Boerwinkle said.

Transferring firearms to another Illinois resident who does not have a valid card is a crime in Illinois. Jeffrey Reinking has indicated to police that he gave his son’s guns back to him, but it is not clear how and when he did so, said Aaron, the spokesman for the Nashville police.